Plaster containing an active agent

ABSTRACT

The invention relates to a plaster containing an active agent, comprising at least one cover membrane and an active membrane which is based on a skin-compatible matrix containing a molecular sieve which is loaded with at least one active agent. The molecular sieve/active agent adduct releases the active agent when the active membrane comes into contact with the skin, in conjunction with the transpired water of the skin. The inventive plaster is characterised in that the molecular sieve/active agent adduct also contains water of crystallisation, to the extent that the molecular sieve is partially hydrated compared to a sufficient basic molar quantity (m) of water of crystallisation, the molecular sieve with the reduced molar quantity (m′) of water of crystallisation being loaded with the active agent (Z, Z 1 , Z 2 ) so that when the active membrane comes into contact with the skin, water is absorbed and the active agent is desorbed, whereupon the water of crystallisation content of the molecular sieve increases. The invention also relates to various suitable embodiments of the plaster containing an active agent and to an advantageous method for producing the inventive plaster containing an active agent.

CROSS REFERENCE TO RELATED APPLICATIONS

Applicants claim priority under 35 U.S.C. §119 of German Application No. 100 13 504.8 filed Mar. 20, 2000. Applicants also claim priority under 35 U.S.C. §365 of PCT/DE01/00687 filed Feb. 23, 2001. The international application under PCT article 21(2) was not published in English.

The invention relates to a plaster containing an active agent comprising at least

-   -   one cover membrane and     -   an active membrane based on a skin-compatible matrix containing         a molecular sieve which is loaded with at least one active         agent, wherein the molecular sieve/active agent adduct releases         the active agent when the active membrane comes into contact         with the skin, in conjunction with the transpired water of the         skin.

Such a plaster containing an active agent is described in, for example East German Patent 278494 A1. The active membrane therein is formed, in particular, from a skin-compatible, pressure-sensitive adhesive, in which the molecular sieve/active agent adduct is incorporated. From this complex, the active agent is released by desorption, caused by diffusion of transpired water of the skin into the pressure-sensitive adhesive. Thereafter the active agent is dissolved and diffuses to the surface of the skin as a function of the composition of the pressure-sensitive adhesive.

The following advantages are associated with the use of plasters containing an active agent in connection with medical treatment:

-   -   Plasters containing an active agent offer an effective         alternative to ointment dressings.     -   Plasters containing an active agent broaden the therapy spectrum         in medicine considerably, especially in dermatology.     -   Prolonged application of plasters containing an active agent is         often more favorable than injections or tablets. Thus they         embody a modern form of “transdermal systems”.     -   Since the active membrane adheres gently, the external         irritations of adhesive bandages are eliminated. Nevertheless, a         firm hold is ensured, in turn leading to good application. These         advantages are evident, in particular, in the treatment of         children.

In connection with a further development, the object of the invention is to provide a plaster containing an active agent that satisfies the following criteria:

-   -   A high active agent concentration directly at the disease focus,         with continuous active agent supply must be ensured. In the         plasters containing an active agent known heretofore, either an         “injection effect” occurred, i.e. the active agent level drops         rapidly, accompanied by a substantial reduction of the         time-release effect of the medication, or the active agent was         released at an uncontrolled rate.     -   The plaster containing an active agent must also be         distinguished by improved penetration behavior in a moist         environment. This is important in that the moist environment         creates ideal conditions for cell growth factors and serves for         immune defense.     -   Furthermore, shorter treatment times at lower medication loads         must be achieved with the plaster containing an active agent,         together with simplified monitoring without clinical         instruction.     -   Finally, in dermatology, for example, the spectrum of medical         applications must be broadened with the plaster containing an         active agent, since some skin diseases (granulomas, keratoses)         can only be treated with plasters containing an active agent.

For the purpose of achieving this object, the inventive plaster containing an active agent is now characterized according to the body of claim 1 in that

-   -   the molecular sieve/active-agent adduct also contains water of         crystallization, to the extent that the molecular sieve is         partially dehydrated compared to a sufficient basic molar         quantity (m) of water of crystallization, said molecular sieve         with the reduced molar quantity (m′) of water of crystallization         being loaded with the active agent, so that when the active         membrane comes into contact with the skin, water is adsorbed and         the active agent is desorbed, whereupon the water of         crystallization content of the molecular sieve increases.

Practical alternative embodiments of the plaster containing an active agent are specified in claims 2 through 19.

Another object of the invention is to provide a method for production of the inventive plaster containing an active agent.

According to the characteristics of claim 20, the method for production of the new plaster containing an active agent is now characterized by the following steps:

-   -   the molecular sieve with a sufficient basic molar quantity (m)         of water of crystallization is partially dehydrated at 300 to         500° C. , preferably 400 to 450° C., for several hours,         preferably 2 to 6 hours;     -   the partially dehydrated molecular sieve with the reduced molar         quantity (m′) of water of crystallization is then loaded with at         least one active agent, thereby forming the molecular         sieve/active agent adduct;     -   the molecular sieve/active agent adduct is now incorporated into         the matrix to form the active membrane;     -   finally, the active membrane is assembled with the cover         membrane to form the plaster containing an active agent.

The foregoing dehydration and/or loading step(s) are/is performed, in particular, in the presence of an inert gas, such as nitrogen. The dehydration and/or loading step(s) are/is preferably performed under normal pressure. The loading step itself can be accomplished by means of a ball mill, for example.

Advantageously, the assembly step is followed by a drying process, which is carried out at 30 to 100° C., preferably 50 to 70° C., for 2 to 6 hours, preferably 3 to 4 hours. In this way, a self-adhesive matrix is formed.

Alternatively, the molecular sieve/active agent adduct can be prepared in such a way that, in combination with a non-adhesive matrix, it triggers the self-adhesive capability of the active membrane.

The invention will now be explained on the basis of exemplary embodiments with reference to schematic drawings, wherein:

FIG. 1 shows the adsorption/desorption mechanism on the basis of two exemplary embodiments;

FIG. 2 shows the adsorption/desorption mechanism on the basis of two molecular sieve/active agent adducts which have different degrees of dehydration.

According to FIG. 1, plaster 1 containing an active agent has the form of a composite comprising a cover membrane 2 and a self-adhesive active membrane 3.

Active membrane 3 in turn comprises matrix 4, in which molecular sieve/active agent adduct 5 is incorporated. In particular, a sodium aluminosilicate of the formula Na₈₆[(AlO₂)₈₆·(SiO₂)₁₀₆ ]·m(m′)H₂O which contains a basic molar quantity (m=276) of water of crystallization in the not yet dehydrated state is used as the molecular sieve. During the partial dehydration step, at least 20%, preferably 40 to 70% of the moles of water are removed. The partially dehydrated molecular sieve with the reduced molar quantity (m′; for example, m′=200) is now loaded with an active agent Z.

During skin contact 6 of active membrane 3, water is now drawn from the skin or from the wound region and taken up (adsorption) by molecular sieve/active agent adduct 5, whereupon desorption of active agent Z takes place. At the same time, the content of water of crystallization in the molecular sieve increases. Thus the molecular sieve regains the water of crystallization that had been removed from it by partial dehydration.

The fact that molecular sieve/active agent adduct 5 basically contains water of crystallization ensures an appropriate moist environment. In this way, desorption of active agent Z by means of water acting as a solvent or dispersant agent is facilitated. In addition, the moist environment creates ideal conditions for cell growth factors and also serves for immune defense.

Examples of plasters containing an active agent are:

-   plaster containing prednisolone as the active agent (to counter     inflammation), -   plaster containing Vitamin A acid as the active agent (to counter     keratosis), -   plaster containing antibiotic as the active agent (to counter     infectious diseases), -   plaster containing an antithrombotic as the active agent (to counter     thrombosis).

A further exemplary embodiment is illustrated in the scope of the same figure. In this case the molecular sieve having a uniform degree of dehydration is loaded with a first active agent Z₁, and a second active agent Z₂, which are present in different degrees of loading, so that molecular sieve/active agent adduct 5 releases active agents Z₁, and Z₂ sequentially upon skin contact 6 of active membrane 3, as illustrated by the different arrow thicknesses. The two active agents have approximately the same molecular weight. The following numerical example will illustrate this. The molecular sieve has a degree of dehydration of 70%. At a total degree of loading with active agents Z₁, and Z₂ equal to 60%, Z₁, accounts for 40% and Z₂ for 20%. By virtue of the greater loading concentration, active agent Z₁, is released more rapidly than active agent Z₂, and therefore the therapeutic effects are staggered in time.

An example of a medical use of this type would be the combination of an antithrombotic (Z₁) with an antibiotic (Z₂), which can also be cited for the exemplary embodiment according to FIG. 2, which will now be presented in more detail.

A first and second molecular sieve 11 and 12 of the same type but different degrees of dehydration are incorporated in matrix 10, as in the following example:

-   molecular sieve type: Na₈₆[(AlO₂)₈₆·(SiO₂)₁₀₆]·m(m′)H₂O -   basic molar quantity (m) before partial dehydration: m=276 -   reduced molar quantity (m′)     -   molecular sieve/active agent adduct 11 containing active agent         Z₃: m′=100     -   molecular sieve/active agent adduct 12 containing active agent         Z₄: m′=200

For approximately equal molecular weights of active agents Z₃ and Z₄, the degree of loading is about the same for each.

Upon skin contact 13 of active membrane 9, active agents Z₃ and Z₄ are released sequentially, once again as symbolized by the arrows of different thickness. In other words, adduct 11 with the greater degree of dehydration will take up water more readily than adduct 12. As a result, active agent Z₃ will be released more rapidly than active agent Z₄, and once again the therapeutic effects will be staggered in time.

Independent of the exemplary embodiments, it is practical if the following parameters apply for plasters 1 and 7 containing an active agent:

-   -   Adducts 5, 11 and 12 are distributed substantially uniformly in         the matrix 4 and 10.         -   Adducts 5, 11 and 12 comprise a proportion of 2 to 20 wt %,             preferably 5 to 10 wt %, specifically relative to the total             mass of active membrane 3 and 9.     -   Matrix 4 and 10 is a polymer material, especially, once again,         an elastomer, a thermoplastic elastomer or a thermoplastic         synthetic material. What is important in this connection is that         these materials form a skin-compatible matrix.     -   Active membrane 3 and 9 has a layer thickness of 0.5 mm to 2 mm,         preferably 1 mm. The layer thickness of the active membrane is         greater than that of the cover membrane.

The plaster containing an active agent is usually enclosed in a sterile package. Alternatively, active membrane 3 and 9 can be covered with a removable protective film.

The values of degree of dehydration and degree of loading cited in the specification and in the claims are relative to the condition after completion of partial dehydration or loading, i.e. before metabolic exchange of water and active agent.

LIST OF REFERENCE SYMBOLS

-   1 Plaster containing an active agent -   2 Cover membrane -   3 Active membrane -   4 Matrix -   5 Molecular sieve/active agent adduct containing active agents Z,     Z₁, Z₂ -   6 Skin contact -   7 Plaster containing an active agent -   8 Cover membrane -   9 Active membrane -   10 Matrix -   11 Molecular sieve/active agent adduct containing active agent Z₃ -   12 Molecular sieve/active agent adduct containing active agent Z₄ -   13 Skin contact 

1. Plaster containing an active agent (1, 7) comprising at least one cover membrane (2, 8) and an active membrane (3, 9) based on a skin-compatible matrix (4, 10), containing a molecular sieve which is loaded with at least one active agent (Z, Z₁, Z₂, Z₃, Z₄), wherein the molecular sieve/active agent adduct (5, 11, 12), releases the active agent upon skin contact (6, 13) of the active membrane, in conjunction with the transpired water of the skin, characterized in that the molecular sieve/active agent adduct (5, 11, 12) also contains water of crystallization, to the extent that the molecular sieve is partially dehydrated at a degree of dehydration of at least 20%, compared to a sufficient basic molar quantity (m) of water of crystallization of at least 100, said molecular sieve with the reduced molar quantity (m′) of water of crystallization being loaded with the active agent (Z, Z₁, Z₂, Z₃, Z₄), so that water is adsorbed upon skin contact (6, 13) of the active membrane (3, 9) and the active agent is desorbed, whereupon the water of crystallization content of the molecular sieve increases, and the molecular sieve is a sodium aluminosilicate of the following formula: Na₈₆[(AlO₂)₈₆×(SiO₂)₁₀₆ ]×m(m′)H₂O.
 2. Plaster containing an active agent according to claim 1, characterized in that the molecular sieve contains a basic molar quantity (m) of water of crytallization equal to at least
 200. 3. Plaster containing an active agent according to claim 1, characterized in that the molecular sieve is a sodium aluminosilicate of the following formula: Na_(86 [(AlO) ₂)₈₆×(SiO₂)₁₀₆]×276 H₂O.
 4. Plaster containing an active agent according to claim 1, characterized in that the partially dehydrated molecular sieve has a degree of dehydration of 40 to 70%.
 5. Plaster containing an active agent according to claim 1, characterized in that the degree of loading of the active agent (Z, Z₁, Z₂, Z₃, Z₄) in the molecular sieve/active agent adduct (5, 11, 12) is smaller than the degree of dehydration of the partially dehydrated molecular sieve.
 6. Plaster containing an active agent according to claim 5, characterized in that the degree of loading is equal to at least 50% of the degree of dehydration.
 7. Plaster containing an active agent according to claim 1, characterized in that the molecular sieve/active agent adduct (5, 11, 12) is distributed substantially homogeneously within the matrix (4, 10) of the active membrane (3, 9).
 8. Plaster containing an active agent according to claim 1, characterized in that the molecular sieve/active agent adduct (5, 11, 12) is present in a proportion of 2 to 20 w t%, specifically relative to the total mass of the active membrane (3, 9).
 9. Plaster containing an active agent according to claim 1, characterized in that the matrix (4, 10) of the active membrane (3, 9) is a polymer material, such as an elastomer, a thermoplastic elastomer or a thermoplastic synthetic material.
 10. Plaster containing an active agent according to claim 1, characterized in that the active membrane (3, 9) has a layer thickness of 0.5 mm to 2 mm.
 11. Plaster containing an active agent according to claim 1, characterized in that the active membrane (3, 9) has a greater layer thickness than the cover membrane (2, 8).
 12. Plaster containing an active agent according to claim 1, characterized in that the molecular sieve having a uniform degree of dehydration is loaded with at least a first active agent (Z₁) and a second active agent (Z₂), which are present in different degrees of loading, so that the molecular sieve/active agent adduct (5) releases the active agents (Z₁, Z₂) sequentially upon skin contact (6) of the active membrane (3).
 13. Plaster containing an active agent according to claim 1, characterized in that at least a first and second molecular sieve of the same type but different degress of dehydration are incorporated in the matrix (10), the first molecular sieve being loaded with a first active agent (Z₃) and the second molecular sieve being loaded with a second active agent (Z₄), specifically having the same degree of loading, so that the first molecular sieve/active agent adduct (11) and the second molecular sieve/active agent adduct (12) release the active agents (Z₃, Z₄) sequentially upon skin contact (13) of the active membrane (9).
 14. Plaster containing an active agent according to claim 1, characterized in that the active membrane (3, 9) is self-adhesive.
 15. Plaster containing an active agent according to claim 14, characterized in that the self-adhesive capability of the active membrane (3, 9) is based on a self-adhesive matrix (4, 10).
 16. Plaster containing an active agent according to claim 14, characterized in that the molecular sieve/active agent adduct (5, 11, 12) is prepared in such a way that it triggers the self-adhesive capability of the active membrane (3, 9) in combination with a non-adhesive matrix (4, 10).
 17. A method for the production of a plaster containing an active agent (1, 7) according to claim 1, characterized by the following steps: the molecular sieve with a sufficient basic molar quantity (m) of water of crystallization is partially dehydrated at 300 to 500° C., for 2 to 6 hours; the partially dehydrated molecular sieve with the reduced molar quantity (m′) of water of crystallization is then loaded with at least one active agent (Z, Z₁, Z₂, Z₃, Z₄), thereby forming the molecular sieve/active agent adduct (5, 11, 12); the molecular sieve/active agent adduct (5, 11, 12) is now incorporated into the matrix (4, 10) to form the active membrane (3, 9); finally, the active membrane (3, 9) is assembled with the cover membrane (2, 8) to form the plaster containing an active agent (1, 7).
 18. Method according to claim 17, characterized in that the dehydration and/or loading step(s) is/are performed in the presence of an inert gas.
 19. Method according to claim 17, characterized in that the dehydration and/or loading step(s) is/are performed under normal pressure.
 20. Method according to claim 17, characterized in that it is followed by a drying process.
 21. Method according to claim 20, characterized in that the drying process is carried out at 30 to 100° C., for 2 to 6 hours. 